Lochinvar KBN 106 noise

Dave_132

I was contacted by a homeowner who has had a lot of banging in his system. The system pressure in within normal limits 12# and all combustion values are good. I heard the noise and isolated the system. I removed the top on the spiro vent as well as the screen and found small pieces of a nylon,Teflon, polymer or plastic material restricting flow. After cleaning it seemed to quiet down but not totally. I attempted to close the webstone flange isolation valves on the boiler pump and they would not move. I am wondering if these valves have failed and perhaps have lodged similar material in the heat exchanger reducing flow therefore causing the banging. Has anyone ever experienced a ball valve disintegrate and cause problems of this nature? I know that the pump is working properly and the right size. Is there an effective way to flush foreign matter from a gianonni heat exchanger?